P0115

Engine Coolant Temperature Sensor Circuit:

Connector: C-71:

CIRCUIT OPERATION
- 5-volt voltage is applied to the engine coolant temperature sensor output terminal (terminal 1) from the PCM (terminal 44) via the resistor in the PCM. The ground terminal (terminal 2) is grounded with PCM (terminal 57).
- The engine coolant temperature sensor is a negative temperature coefficient type of resistor. It has the characteristic that when the engine coolant temperature rises the resistor decreases.
- The engine coolant temperature sensor output voltage increases when the resistor increases and decreases when the resistor decreases.

TECHNICAL DESCRIPTION
- The engine coolant temperature sensor converts the engine coolant temperature to a voltage and output it.
- The PCM checks whether this voltage is within a specified range.
In addition, it checks that the engine coolant temperature (signal) does not drop while the engine is warming up.

DTC SET CONDITIONS

Check Area
- Two seconds or more have passed since the engine was started.

Judgement Criteria
- Engine coolant temperature sensor output voltage has continued to be 4.6 volts or higher [corresponding to a coolant temperature of -45° C (-49° F) or lower) for two seconds.
or
- Engine coolant temperature sensor output voltage has continued to be 0.1 volt or lower [corresponding to a coolant temperature of 140° C (284° F) or higher] for two seconds.

Check Area, Judgement Criteria
- Engine coolant temperature sensor output voltage increased from a value lower than 1.6 volts to a value higher than 1.6 volts [coolant temperature decreases from a higher than 40° C (104° F) temperature to a lower than 40° C (104° F) temperature].
- Then the engine coolant temperature sensor output voltage has continued to be 1.6 volts or higher for five minutes.

Check Area, Judgement Criteria
- About 60 - 300 seconds have passed for the engine coolant temperature to rise to about 10° C (50° F) after starting sequence was completed.
- However, time is not counted when fuel is shut off.

Check Area
- Engine coolant temperature was 7° C (44.6° F) or more immediately before the engine was stopped at the last drive.
- Engine coolant temperature was 7° C (44.6° F) or more when the engine started.

Judgment Criteria
- Engine coolant temperature fluctuates within 1° C (34° F) after five minutes have passed since the engine was started.

- However, time is not counted if any of the following conditions are met.
1. Intake air temperature is higher than 60° C (140° F).
2. Volume air flow sensor output frequency is 70 Hz or less.
3. During fuel shut-off operation.

- Only one monitor during one drive cycle.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Engine coolant temperature sensor failed.
- Open or shorted engine coolant temperature sensor circuit, or loose connector.
- PCM failed.

DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)

CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.




STEP 1. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.

- The engine coolant temperature and temperature shown with the scan tool approximately match.

It they don't match, go to Step 2.

If they match, it can be assumed that this malfunction is intermittent. Refer to vehicle level Testing and Inspection.




STEP 2. Check the engine coolant temperature sensor.

1. Disconnect the engine coolant temperature sensor connector A-67.
2. Remove the engine coolant temperature sensor.

3. With the temperature sensing portion of engine coolant temperature sensor immersed in hot water, check resistance.

Standard value:
2.1 - 2.7 kohms [at 20° C (68° F)]
0.26 - 0.36 kohms [at 80° C (176° F)]




4. Apply 3M(TM) AAD part number 8731 or equivalent on the screw section of the engine coolant temperature sensor.

5. Install the engine coolant temperature sensor, and tighten to the specified torque.
- Tighten the engine coolant temperature sensor to 29 N.m (22 ft-lb).

If within specifications, go to Step 3.

If not within specifications, replace the engine coolant temperature sensor. Then go to Step 6.




STEP 3. Check the circuits at the engine coolant temperature sensor connector A-67.

1. Disconnect connector A-67 and measure at the harness side.
2. Turn the ignition switch "ON".

3. Measure voltage between terminal 1 and ground.
- Voltage should be between 4.5 and 4.9 volts.

4. Turn the ignition switch "OFF".




5. Check for continuity between terminal 2 and ground.
- There should be continuity (0 ohms).

If any check above does not meet the specifications, go to Step 4.

If all checks above meet the specifications, repair or replace engine coolant temperature sensor connector A-67. Refer to vehicle level Testing and Inspection. Then go to Step 6.







STEP 4. Check the harness wire between engine coolant temperature sensor connector A-67 and PCM connector C-90.

NOTE: After inspecting intermediate connector C-71, inspect the wire. If intermediate connector C-71 is damaged, repair or replace it. Refer to vehicle level Testing and Inspection. Then go to Step 6

If the wire between engine coolant temperature sensor connector A-67 and PCM connector C-90 is not damaged, go to Step 5.

If the wire between engine coolant temperature sensor connector A-67 and PCM connector C-90 is damaged, repair it. Then go to Step 6.




STEP 5. Check harness connector C-90 at the PCM for damage.
If harness connector C-90 is damaged, repair or replace it.Refer to vehicle level Testing and Inspection.

If harness connector C-90 is in good condition, replace the PCM.

Then go to Step 6.

STEP 6. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern.Refer to Procedure 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that a diagnostic trouble code is not being output.